The present invention relates to plasticized vinyl chloride polymer compositions. More particularly, the present invention relates to vinyl chloride polymer compositions plasticized with meta-tertiary-butylphenyl diphenyl phosphate.
Various phosphate esters are known to be useful as plasticizers for vinyl chloride polymer compositions. One of the first phosphate esters recognized as being useful for this purpose was tricresyl phosphate. The relatively short supply of cresols, from which tricresyl phosphate is prepared however, made it necessary to develop alternative plasticizers. One such alternative was tri(2-ethylhexyl)phosphate. This compound imparted a low temperature flexibility to polyvinyl chloride which was even better than that imparted by tricresyl phosphate, but, unfortunately, the permanence of this plasticizer is less than desirable.
Another ester suggested as being a suitable substitute for tricresyl phosphate, is a phosphate ester disclosed in U.S. Pat. No. 3,931,091 and represented by the structural formula (C.sub.6 H.sub.5)x(m-C.sub.2 H.sub.5 C.sub.6 H.sub.4)yPO.sub.4 wherein x is 1 or 2 and y is 1, 2 or 3 and the sum of x and y is 3. These phosphate esters, which contain at least one m-ethylphenyl group, are said to provide outstanding low temperature flexibility.
More recently it has been disclosed, in U.S. Pat. No. 4,139,487; that the presence of alkyl substituents in at least one of the aryl groups of triaryl phosphates provides improved performance of the triaryl phosphates as plasticizers for vinyl chloride polymers, particularly with respect to low temperature flexibility. The patent teaches that the presence of an isopropyl or sec-butyl group is particularly advantageous and that the presence of alkylphenyl groups containing tertiary carbon atoms is less preferred. Meta-isopropylphenyl diphenyl phosphates are mentioned as being most preferred.
While the state-of-the-art has developed to a point where plasticizers are now available which are relatively effective, a tremendous growth in the use of vinyl chloride polymer compositions and the development of new fields of application for the same presents a need for new plasticizers which are even more effective than those presently available.